Rotary kilns generally are defined as an inclined, large diameter, elongated rotating drum having a stationary in-feed hopper and exhaust stack at the upper end and a stationary out-feed materials collection hopper at the lower, or fired, end. Seals are generally provided at each end for the obvious reasons of maintaining heat, gas, and material particles within the kiln.
Known rotary kiln seals routinely utilize some form of biased heat and abrasive resistant material to bridge the gap between the rotary drum and the stationary in-feed and out-feed housings. Since the rotary drum radius constantly varies relative to its longitudinal centerline due to non-uniform heat within the drum, material weight, etc., the diameter of the drum is distorted. Allowing the drum seals to be displaced as necessary and still maintain a good seal is essential in order to compensate for such distortion. Further, since the seals are often subjected to high heat, friction, and abrasion, the seal material is usually a composite of materials.
A great many of the rotary kiln seal systems are not intended to provide a complete 100% seal. Such seals that allow some leakage of gas and material particles do so in order to allow for some atmospheric intrusion to improve combustion. It has been found that leakage of heat and material particle build-up around and between the seal segments prevents or disrupts any distortion compensation capabilities that may be used. The economics involved in cleaning and replacing seal components is a major factor in kiln maintenance. Therefore, there is a need for a rotary kiln distortion compensation seal arrangement that provides long life and is effective against high heat and material particle buildup.